The heading of memorandums is designed to allow a reader
to understand what he or she is looking at, and decide quickly whether
he or she should read it. The heading has four or five parts, appearing
in this order. The "subject line" should be brief, but clear.

To:

From:

Subject:

Date:

cc:

purpose

Because many messages cross a reader's desk (or computer
screen) daily, the first thing she is likely to ask upon seeing one
is "Should I read this?" The "purpose" section answers that question.
A very direct opening like "The purpose of this memo is to ..." is
perfectly acceptable. It may be addressed to me.

summary

The summary is a brief recounting of the entire memo,
including discussion/background, conclusions, and recommendation.
Its placement as the second section allows a reader who does not need
to know the details to stop reading.

background/discussion

The discussion/background describes the method by which
the conclusion was reached. This section provides details of the subject
and the justification for the conclusion. In almost all cases this
is the longest section of the memo -- (eg., five paragraphs of an
eight-paragraph memo, or two pages of a three-page memo). It is directed
to those who need to know details -- laboratory assistants and clerical
staff, for instance.

In the case of a progress report, this section will include estimated
costs, possible personnel, available facilities and supplies. It may
take a narrative form.

conclusion/action

This makes some sort of conclusion from the issues
and problems described in the "Background/Discussion" section. It
also describes where you intend to go from here.